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Mysterious cloud absorbers driving the climate of the Venusian albedo



  Mysterious cloud absorber driving the Venusian albedo, climate
A composite image of the planet Venus from the point of view of the Japanese probe Akatsuki. Credit: Japan Aerospace Exploration Agency

Like planets in our solar system, Venus is one for the textbooks.

Although Venus is about the size of the Earth, it is a terrestrial planet with a similar composition to our planet and is approximately the same proximity to the Sun. But the parallels pretty much end there. Venus is much hotter ̵

1; near 460 degrees Fahrenheit (860 degrees Fahrenheit) on the surface – due to a runaway greenhouse effect caused by a thick, carbon dioxide-rich atmosphere and a cloud cover consisting mainly of sulfuric acid droplets. The planet turns in the opposite direction of the earth (the sun rises in the west), and its surface has never been seen by the human eye, as it is completely obscured by the shores of opaque, highly reflective clouds.

But like the Earth The weather in Venus is determined by solar radiation and is strongly influenced by changes in the reflection properties or the albedo of the clouds that surround the planet. Thanks to an international research team using a series of satellites to study the long-term fluctuations of the Venus albedo in ultraviolet light, a better picture of the weather has now emerged and how it is affected by changes in the reflectivity of the clouds. The new study was published today (August 26, 2019) in the Astronomical Journal .

"The difference between the Earth and Venus is that most of the solar energy is absorbed near the ground on Earth. On Venus, most of the heat is deposited in the clouds," explains Sanjay Limaye, a planetologist the University of Wisconsin-Madison and co-author of the new study.

What is strange about the clouds of Venus? are unlike anything on Earth – is that in these clouds are mysterious dark spots, which scientists call "unknown absorbers", since the tiny particles that make up the stains, most of the ultraviolet and part of the ultraviolet absorbing and thus influencing visible light from the sun The albedo and energy budget of the planet.

The patches were first observed by ground-based telescopes more than a century ago. They ebb and flow with time and change their distribution and contrasts.

"It has been suggested that the particles that make up the dark spots are ferric chloride, sulfur allotropes, sulfur dioxide, etc., but none of them have yet satisfactorily explained their formation and absorption properties," explains Yeon Joo Lee, the lead author of the new report.

On the other hand, Limaye notes that the particles are about the same size and the same size as light-absorbing properties as microorganisms in the earth's atmosphere, and scientists, beginning with the well-known biophysicist Harold Morowitz and the astronomer Carl Sagan, have long speculated that the shady spots in the clouds of Venus are actually microscopic life. [19659005] Regardless of their composition, Venus' "unknown absorbers" have, according to the new measurements of the albedo of the planet, a feat that was led by Lee of the Technical University of Berlin, effect n the weather of the planet. Lee and her colleagues, including Limaye, studied changes in the Venus albedo from more than a decade of UV observations of the planet with instruments aboard the Venus Express, Akatsuki and Messenger planetary probes and the Hubble Space Telescope.

Between 2006 and 2017, the Venus Albedo, the measure of ultraviolet light reflected back into space, halves before it comes to a rebound. These changes in the albedo of the planet caused large fluctuations in the amount of solar energy absorbed by the clouds, and consequently in the circulation of the Venus atmosphere. Specifically, the albedo changes help explain variations in the planetary atmosphere's high activity, which has the phenomenon of "superrotation" driven by winds at speeds in excess of 200 miles per hour.

Takeshi Horinouchi of the Japanese Hokkaido University The co-author of the new Astronomical Journal and expert on the weather in Venus says that the new results of the changes in the albedo of the planet represent a link between the solar heat and the strong gusts that support the dynamics of the upper atmosphere of the planet.

"What really impressed me about this work is that the climate of Venus, as well as Earth, has decades of climate variability," says Venus expert Mark Bullock of the Southwest Research Institute, who was not involved in the new study. "Even more amazing is that the magnitude of climate change on Venus is much greater than the long-term fluctuations of the earth."

"That's a remarkable result," adds Limaye. "It indicates that something is changing, we can see the change in brightness, if the albedo changes, something is driving those changes, the question is, what is the cause?"

The ups and downs of the mysterious dark patches At the top of Venus' clouds, the "Unknown Absorbers" are at the top of the list of suspects and could actually play a major role in these changes, say Lee and Limaye. Haze over the clouds, which is composed of smaller particles, can make Venus appear even brighter.

Weather and climate, whether on Earth or on Venus, are driven by solar radiation, including ultraviolet radiation that we can not see. And clouds and their changing ability to reflect light have a tremendous impact.

"Does solar ultraviolet light affect the cloud cover of Venus? Influence cosmic rays – subatomic particles from space that continuously rain on all planets – cloud cover by triggering cloud formation – would planetary sulfur dioxide affect the formation of sulfuric acid clouds?" Lee asks.

The new study helps to clarify the dynamics of the Venus albedo and the potential impact of the enigmatic dark patches that travel over the peaks, the cloud banks of the planet, if not their composition. The results, however, may only arouse the interests of scientists concerned with the planet and its weather. This could provide new insights into the Earth, climate and weather.


New research deals in more detail with Venus clouds


Further information:
Yeon Joo Lee et al. Long-term variations of Venus' 365 nm albedo, observed by Venus Express, Akatsuki, MESSENGER and the Hubble Space Telescope, The Astronomical Journal (2019). DOI: 10.3847 / 1538-3881 / ab3120

Provided by
University of Wisconsin-Madison




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Mysterious Cloud Absorber as a Drive of the Venusian Albedo, Climate (2019, August 27)
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